Normal vascular endothelial cells in culture will be studied with respect to several cellular and molecular parameters of the control of proliferation. Specifically, growth responses, proliferative capacities, cellular "adhesion", and interaction with neoplastic cells will be investigated. Macromolecular precursor uptake and incorporation, polysome levels, rTNA turnover and messenger RNA metabolism will be investigated in early and late passage cultures derived from fetal and adult tissue.